Calipering method and apparatus



Oct. 4, 1955 R. F. MONTGOMERY ETI'AL 2,719,363

CALIPERING METHOD AND APPARATUS Filed Jan. 19, 1953 5 Sheets-Sheet l ATTORNEYS Oct. 4, 1955 R. F. MONTGOMERY ETAL 2,719,363

CALIPERING METHOD AND APPARATUS Filed Jan. 19,1953 5 SheetsSheet 2 ATTORNEYS Oct. 4, 1955 R. F. MONTGOMERY ETAL 2,719,363

CALIPERING METHOD AND APPARATUS 5 Sheets-Sheet 3 Filed Jan. 19, 1953 u n I T INVENTORS ATTORNEYS Oct. 4, 1955 Filed Jan. 19, 1953 R. F. MONTGOMERY ETAL 2,719,363

CALIPERING METHOD AND APPARATUS 5 Sheets-Sheet 4 E 9 31 29 In I X? \5 y I r a 317' A4? 77%" I 7F\ IIIIHUK IN VENTORS ATTORNEYS Oct. 1955 R. F. MONTGOMERY ETAL 2,719,363

CALIPERING METHOD AND APPARATUS Filed Jan. 19, 1953 5 Sheets-Sheet 5 INVENTORS WMFW,

BY il J ATTORNEYS United States Patent CALIPERING METHOD AND APPARATUS Richard Franklin Montgomery, Snyder, and Nicolaas L. H. Knot, ()dessa, Tex. Application January 19, 1953, Serial No. 331,916

24 Claims: (Cl. 33178) Our invention relates to the art of calipenng a well bore, and more specifically provides a novel method of running the caliper and novel apparatus for carrying out said method. g

The principal object of our invention is to provide a novel and greatly improved method of running a caliper within a drilled bore. It is well known that the removal of a drill string from a bore several miles deep is a timeconsuming operation which in itself contributes relatively little information to the operators. In all known methods now used, when the'bore is completed it is necessary to pull all of the drill string out of thebor'e and then to rim a caliper down into the bore on a wire line, the log generally being recorded on the surface by the aidof electronics. According to the present invention; however, a special section of pipe, hereinafter referred to asthe substitute, is inserted between the drill bit and the lowermost drill collar prior to the beginning of the drilling operation. When this operation has been completed and the desired depth of bore established; the operator then opens the kelly joint and inserts our novel c'a-lipertool into the pipe string and pumps the tool downwardly in the string until it reaches and enters the substitute.- caliper tool in the bore of the substitute triggers a latch mechanism thereby releasing an inner barrel within; the substitute and causing said barrel to drop downwardly a short distance with respect to said substitute; The inner barrel has slots through to wall, and a plurality of caliper arms attached to said tool pivot outwardly through said slots and engage the walls of the drilled bore, whereby the tool will record a running log of the size ofthe bore as the substitute and drill string assembly are moved upwardly within the bore during removal of the drill string therefrom. When the assembly has thus-been withdrawn, the caliper tool is recovered from within the substitute and the operator removes from the tool a chart whereon is graphically inscribed a running log of the diameter of the bore.

The arrival of the An important feature or novelty of our invention relates to the above mentioned pum ing of the caliper tool downwardly through the drill string whereby said tool travels in a smooth bore all the way down-to the substitute. This feature eliminates the possibility of the tool sticking or getting lodged or hung up as it travels downwardly. The tools of the prior art when lowered on a wire line into the bore have a tendency to encounter irregularities within the bore and bridge thereacross, particularly when the bore drilled into the earth is not straight.

Another important object of our invention is to provide an engagement between the substitute and'the caliper tool having an annular clearance to establish fluid passage ways so that when the caliper tool is in place within the substitute, fluid circulation may be maintained through the pipe string to provide the operator with complete control of the bore against'blowouts.

Another important object of our invention is to' provide a substitute having two telescoping barrel sections, the inner section-normally beingret-raeted :within the outer sec- 2,719,363 Patented Oct. 4, 1955 "ice the two barrel sections are in their elongated position, the

engagement changes from a nonrotatable engagement to a ball-bearing engagement so as to permit the outer and inner barr'el sections to freely rotate with respect to each other. The advantage of this change of engagement from nonrotatable to rotatable is that when the two barrel sections are in their mutually elongated position and the caliper arms are engaging the walls of the bore, the pipe string may be rotated by the operator for the purpose of disconnecting the stands of pipe as they are withdrawn from the bore, thereby allowing'the caliper arms to stand motionless against the Well bore while the pipe string is being'rotated to disconnect a stand.

Another important object of our invention'is to provide an engagement between the caliper tool and the inner barrel whereby the tool may telescope upwardly in said barrel so that the caliper arms will not be damaged in the event the pipe string should be lowered through a short distance as the tool joints are unscrewed at the surface during removal of the successive stands of pipe.

Another primary object of our invention is to provide a" calipering and recording tool adapted to be received in thesubstitute and having a plurality of caliperarms each of which is moved'in accordance'with the variation of the diameter of the drill bore as the arms travel upwardly therein. Each of these arms is operatively connected to a measuring piston acting upon a confined liquid within the recording tool. The total volume of space occupied by theconfined liquid is always constant and the respective measuring pistons, as they are moved by the associated arms,- c'ause the distribution of the fluid on each side of a recording piston to fluctuate, thereby driving the recordingpiston upwardly or downwardly within the recording tool in accordance with the instantaneous summation of the positions of all of the measuring pistons. The recording piston is linked to a recording stylus, which stylus presses against a moving chart and records thereon the average diameter of the well bore in accordance'withthe summation of the readings supplied by all of the aforementioned caliper anns, the moving chart' being driven by a clock mechanism contained Within the recording tool.

The advantage of this assembly is that a log of the diameter of the well bore may be accurately obtained because of the fact that the various caliper anasw rk independently of each other and because of the fact that the hydraulic recording system provides a reading which is proportional to the summation of the instantaneous positions of all the arms. Thus, if the well bore is crooked and the caliper is lying against one side of the bore so th'a-tthe caliper arms are fully retracted on that side, the arms opposite the side of the caliper contacting the well here will be further expanded to compensate for the fact that the caliper is not centered within the bore at that particular moment. 7

Another important advantage of the present invention is' that static-electric charges within the here will not affect readings of the recording tool, since the latter operates by mechanical and hydraulic means rather than by electrical recording means.

Other objects and advantages of our invention will become apparent during the discussion of the drawings, wherein:

Fig. lis' a section through a well bore, showing a drill string including the aforementioned substitute interposed in the string adjacent the drill bit, the substitute being in telescopically retracted position.

Fig. 2 is a section through the well bore, showing the drill string pulled upwardly a distance sufiicient to permit the inner barrel section of the substitute to elongate downwardly with respect to the outer barrel section and showing the caliper arms extended outwardly and engaging the walls of the bore.

Figs. 3, 3a and 3b illustrate a longitudinal section through the ealipering and recording tool, showing the caliper arms connected with the measuring pistons, through associated cam followers and showing the chart drums operatively engaged with the clock and drive mechanism, the latter being illustrated only schematically.

Figs. 4, 4a and 4b illustrate another longitudinal section through the recording tool, showing a clear illustration of the chart drive and stylus linkages.

Figs. 5 and 5:: illustrate a longitudinal section through the substitute showing the barrel sections retracted and latched, and showing the drill bit connected to the inner barrel section.

Fig. 6 is a longitudinal section through the substitute, showing the respective inner and outer barrel sections retracted, and showing the tool located in a position where it has just triggered the latch holding the inner barrel section retracted within the outer barrel section.

Fig. 7 is a longitudinal section through the substitute. showing the inner barrel section in elongated position with respect to the outer barrel section, and showing the calipering and recording tool seated within the inner barrel section with the caliper arms extended through the slots and engaging the walls of the bore.

Fig. 8 is a section view taken along line 88, of Fig. 3a.

Fig. 9 is section view taken along line 99 of Fig. 3a.

Fig. 10 is section view taken along line 1010 of Fig. 3a.

Fig. 11 is a section view along line 1111 of Fig. 3a.

Fig. 12 is a section view along line 1212 of Fig. 3a.

Fig. 13 is a section view along line 1313 of Fig. 31).

Fig. 14 is a partial section view along line 1414 of Fig. 5.

Fig. 15 is an enlarged partial section View along line 15-15 of Fig. 7.

Fig. 16 is a section view along line 1616 of Fig. 4.

Fig. 17 is a section View along line 1717 of Fig. 4.

Referring now to the drawings, Figs. 1, 2 and 7 illustrate the drilling and calipering assembly within the bore B, Figs. 1 and 2 illustrating a drill string S having a drill bit D at the bottom thereof and having interposed within the string directly above the bit D the telescoping and rotating substitute 1.

The substitute By reference to Figs. 5, 5a, 6 and 7 it will be seen that the substitute 1 includes an outer barrel section 2 and a telescoping inner barrel section 3. The respective barrel sections 2 and 3, when in their mutually retracted position, engage each other nonrotatively at the splines 2a and 3a, and also engage each other at the intermeshing teeth 2b and 3b, the splines and teeth being provided so as to permit transmittal of torque from the drill string S through the substitute to the drill bit D during the drilling operation. The outer and inner barrel sections are maintained in their mutually retracted position by the latches 30 which engage the annular shoulder 2c, said latches being yieldably maintained in engagement with the shoulder 20 by the leaf springs 3d and said latches having at their lower ends inward projections 32, Fig. 5.

By reference to Figs. 5, 5a, 6 and 7 it may be seen that the inner barrel section 3 has an annular series of axially disposed slots 3 which slots serve the purpose hereinafter discussed.

By reference to Figs. 5, 6, 7 and 14 it will be seen that the inner barrel 3 has mounted near its upper end a series of ball bearings 5, which ball bearings are inoperative when the outer and inner barrel members 2 and 3 are in mutually retracted position but which ball bearings engage the annular shoulder 2d when the outer and inner barrels 2 and 3 are in their extended position as shown in Fig. 7, the ball bearings 5 being clearly shown in Fig. 14. When the inner and outer barrel members 2 and 3 are in extended position the splines 2a--3a and the teeth 2b-3b are disengaged so that the inner barrel 3 may freely rotate within the outer barrel 2, the former being vertically supported by the latter by the engagement of the ball bearings 5 with the annular shoulder 2d.

The calipering and recording too! By reference to the drawings, Figs. 3, 3a, 3b, 4, 4a, and 4h it will be seen that at the lower end of the recording tool 6 are a series of downwardly extending cam followers 7. Above the cam followers 7 and fixed thereto are measuring pistons 70, each of the pistons 7a having an upwardly extending connecting rod 7b screwed into an upper measuring piston 7c, and each of the connecting rods 7b passing through a sleeve 7d secured against longitudinal displacement by means of a set screw 7e. Above each measuring piston 7c is a compressed coil spring 9, which spring operates to press the associated piston 7c downwardly within its associated cylinder 6!), which cylinder is vented outside of the body of the recording tool 6 as at the vent Go.

By reference to Fig. 11 it will be seen that the space within the cylinders 6b and lying between each sleeve 7d and each upper measuring piston 70 is connected with an axial duct 6d by means of short ducts 6e. Similarly, it will be seen that the space within the cylinders 6b and lying between each sleeve 7d and each lower measuring piston 70 is connected with the longitudinal duct 6k by means of a plurality of short ducts 6111, Fig. 12.

Figs. 4 and 4a show that the cylinders 6b and the ducts 6d, 66, 6k, and 6m are filled with a liquid. This liquid presses against the lower end of a recording piston 10 in duct 6k, and also presses against the upper end of the recording piston 10 as at 6r, Fig. 4.

It should now be apparent that when a cam follower 7 is moved upwardly, the volume below the associated pistons 7c (and therefore the volume of liquid within the ducts 6d and 6e) will be increased, and that by the same movement the volume of liquid within the cylinder 611 above the pistons 7a, (and therefore in the ducts 6m and 6k) will be decreased so that the liquid will press against the lower end of the recording piston 10 and move it upwardly. Conversely, when a cam follower 7 is moved downwardly the liquid will press against the upper end of the recording piston 10 at 6r and drive the latter downwardly.

Figs. 11 and 12 show that all of the cylinders 6b are connected together both in the vicinity of the ducts 6e and in the vicinity of the ducts 6m, and therefore the amount of motion transmitted to the recording piston 10 by the liquid will be proportional to the instantaneous summation of the movement up or down of all of the cam followers 7.

At the lower end of the recording tool 6 is mounted a caliper arm assembly, Figs. 3a, 3b, 4b, 9, 10, and 13. This assembly includes the caliper arms 8 pivoted at their upper ends on pins 8a secured in a mounting web 812, the latter being attached to the lower end of the re cording tool 6 by screws 8c. Each arm 8 has a cam surface 8d against which a cam follower 7 is pressed by its associated spring 9, the spring not only maintaining the follower 7 in contact with the cam 8d but also yieldably urging the associated arm 8 outwardly to contact the bore B as shown in Fig. 2. The lower end of each arm is provided with a tip 82 rounded on one side to contact the bore B and having an inwardly extending projection 81, these projections nesting together to mutual- Iy support the arms- 8;-when the latter are retracted together as shownin Figs. 3b and 13.

At the upper end of the system of ducts, Fig. 4, is a plug 11 adapted to confine the liquid within the ducts and having a screw 11a through which the liquid may be replenished and through which air may be removed from within the ducts. The plug 11 also has a bore 11b through which a hollow recording shaft 12 passes, the shaft being attached at its lower end to the recording piston IO-and'carrying at its upper end a recording stylus 12a-.- This shaft also has a small breather port 12b communicatingthrough the'center of the shaft 12 with a duct 100 so as tovent' the chamber b, which chamber is normally free of liquid.

The chart chamber 6s-houses-the data-recording mechanism. and has an access door- 6p to permit installation or removal of the charts C from the chart. rollers 13' and 13a. It will be noted in Fig. 1 6 that the chart C travels from the roller 13- around'theidlerrollers-13c and 13d and on to the takeup' roller 13a, the stylus 12a recording the various positions at any particular instant of time by marking the chart C againstfthe idler roller 130, the stylus being atall times spring-loaded by the leaf spring 12d. A groove 6x isprovided in the door 6p and supports the upper end 12d of theshaft L2,.Fig; 16. I

A rubber drive roller 14 is supported on bearings 14a fixed toleaf springs 14b which springs force the rubber roller 14 against the chart rollers-13-13a. The rubber roller 14 is driven through afiexible cable 140, which in turn is driven by a series of gears 14d, one of which is driven by a clock mechanism 15 (shown only schematically.)

Figs. 3 and 7 show that at the upper end ot the tool 6 is a-plug 4, threadedly secured in the tool as at threads 4a. The plug 4 has an annular series of spacedbosses 4b for the purpose herein-after discussed, and in addition a fishing tip4c may be provided in case itshouldbecome necessary to retrieve the tool 6 before the whole pipe string S has been removed from the drilled bore.

The engagements between the various parts of the substitute 1 and between the various parts of the recording tool 6 are provided with annular grooves adapted to receive rubber O-rings R to prevent seepage of the various fluids through the joints with. which these rings are associated.

Operation In calipering the diameters of abore B, the operator places the rotating and telescoping substitute 1 in the pipe string S above the drill bit D, the inner barrel portion 3 being telescoped upwardly into the outer barrel portion 2 and latched therein by the latch 3c, at which time the splines 2a3aand teeth'2b'3b' mutually intermesh to prevent relative rotation between the barrels 2 and 3. With this assembly in the pipe string, the operator proceeds to drill the bore B, into the earth, and when he has drilled the bore to its desired depth he retracts thedrill string upwardly a few feet from the bottom of the bore B, opens the kelly joint and inserts the calipering and recording tool 6 into the pipe string. Hethen closes the kelly joint and starts the pumps to pump the tool 6 downwardly within the pipe string 8- so that it arrives in the relative position shown in Fig. 6.

Upon. continued pumping'the recording tool 6'will proceed downwardly and into the tubular center 3g of the inner barrel section 3, at whichtime the lower end of the tool 6 will trip the projections 3e and release the latches 3c, thereby permitting the inner barrel portion to drop downwardly with respect to the outer barrel portion 2 until the ball bearings 5 rest upon the annular shoulder 2d. Continued pumping will force the recording'tool 6 further downwardly within the tubular center 3g of the inner barrel 3, at which time the bosses 45 at the upper end of the recording tool 6'will be fitted snugly against the conical surface 3'h'ythe bosses 4bserving to greases '6 support the tool 6 longitudinally positioned as shown' in Fig. 7.

The upper end of the tool 6 is provided with guide grooves 6y, as shown in Figs. 6' and 7, which guide grooves contact the spring fingers 3y, Fig. 5, at the upper end of the inner barrel portion 3 so that as'the guide grooves 6y proceed downwardly with respect to the spring fingers 3y the tool body will be rotated until the arms 8 at the lower end thereof are properly aligned with the slots 31 in the inner barrel 3;

When the recording tool 6 thus seats within the inner barrel portion 3, the operator will be informed of the fact by a rise in pressure as the tool 6 first enters the inner barrel portion 3 and by a drop in pressure as the tool 6 releases the latches 3c and the inner barrel'3 elongates with respect to the outer barrel 2-, Fig. 7, the operator then commences withdrawal of the pipestring from the bore. Generally the string will be withdrawn in stands of approximately three lengths ofpipe each, and asthe string is withdrawn upwardly the'feeler members 8e on the lowerends of the caliper arms 4 will be moved inwardly and outwardly according to the various diameters of bore B encountered. The inward and outward pivoting of the arms 8 causes axial upward or downward motion of the cam followers 7 and the associated pistons 7a and 7c. Axial fluctuation of the location of these pistons causes the vo-lnmeof liquid within the respective ducts 6d and 6k to fluctuate in accordince with the instantaneous summation of the displacement of each of the three groupsof pistons-,thereby driving the recording piston 10, shaft 12 and stylus- 1 2a upwardly and downwardly with respect to the chart C.

As stated above, the chart is moved by the chart rollers 13 and 13a, rotated at a constant rate by the clock mechanism 15; and as the drill string is removed, stand by stand, the chart C will show the summation of the instantaneous deflections of the various caliper arms 8.

Moreover, each time that the upward travel of the drill string is interrupted for the purpose of unscrewing a standof pipe, the chart C will indicate a straight line during the interval that the stand is being unscrewed, since the caliper arms 8 will be standing still with respect to the walls of the bore atthattime.

The recording and calipering tool is free to ride upwardly within the passage 3g of the'barrel 3, so that as the tool joints are unscrewed and the" drill string accordingly lowered in the bore by the length of the threads on the tool joints, the tool 6' may telescope upwardly with the inner barrel 3 to prevent bending or breaking of the arms 8. As'pointed out above, the pipe string S and associated outer barrel portion- 2 may be rotated with respect to the inner barrel portion 3, which inner portion is supported from above only in the ball'bearings 5 on the shoulder 2d. Thus as the pipe string is rotated the caliper arms 8 stand still within the bore, thereby preventing damage thereto.

By inspection of Figs. 6' and 7 it will be apparent that the outer periphery of the recording tool 6 is spaced from the tubular center 3g of the inner barrel portion 3, thereby permitting circulation of the drilling mud between said two members at all timesso that the operator will have suflicient control to prevent blowouts.

When the drill string has been entirely removed from the well the marked chart C may be removed from the tool 6' and-may be replaced by a new chart simply by unscrewing the upper casing 61 from the lower casing 6v of the recording tool 6' and by opening the door 6p which leads into the shart chamber, Fig. 16'.

We do not limit our invention to the exact form shown in the drawings, for obviously changes may be made therein within the scope of the claims.

We claim:

1. In a drill string terminating at its lower end in a bit for drilling a bore, a caliper assembly comprising an outer barrel supported by said string; an inner barrel retained within said outer barrel and telescopically engaged therewith, said barrels each having a liquid passage'therethrough and said inner barrel supporting said bit and having a series of axially disposed annularly spaced slots through its wall, the outer barrel sheathing said slots when said barrels are in mutually retracted position; complementary projections carried by said respective barrels and meshing when the latter are retracted, said meshed projections transmitting torque from said string to said bit during the drilling operation; latch means for releasably maintaining said barrels mutually retracted; and a calipering and recording tool having a series of axially disposed annularly spaced caliper arms pivoted at their ends thereto, and having measurement recording means operatively associated with said arms, said tool being pumped downwardly in said string when the drilling operation is concluded and tripping said latch means to permit elongation of said telescoping barrels to unsheath said slots, said tool lodging in said inner barrel with said caliper arms engaging said well bore through said slots, whereby upon withdrawal of said string upwardly in the well said arms will measure the diameter of said bore and transmit said measurements to said recording means.

2. In a device as set forth in claim 1, said calipering and recording tool having outstanding annularly spaced bosses around its upper end; said inner barrel having a conically flared mouth at the upper end of its liquid passage, and said bosses engaging said flared mouth to arrest downward movement of said tool; and orienting means for turning the tool as it enters said liquid passage to align said arms with said slots, said tool being smaller in diameter than said liquid passage to permit liquid circulation to be maintained at all times through the drill string.

3. In a device as set forth in claim 1, anti-friction bearing means carried by said barrels and operatively engaging when the latter are in elongated position, whereby said supporting string and associated outer barrel can be freely rotated with respect to said inner barrel and said arms, said tool being capable of riding upwardly in said inner barrel to permit the drill string to be lowered in the bore through short distances during withdrawal therefrom without damage to said arms.

4. In a device as set forth in claim 1, said tool comprising a body, having said caliper arms pivoted to its lower end, said arms each having a cam surface at its upper end; a cam follower contacting each cam surface and reciprocably mounted adjacent to an associated cylindrical bore in the body; a measuring piston in each cylindrical bore connected for unitary axial displacement with its associated cam follower, each measuring piston dividing each cylindrical bore into upper and lower portions, the respective upper portions being interconnected and the respective lower portions being interconnected; a recording piston movable within a recording cylinder, said upper portions being connected with one end of said recording cylinder, and said lower portions being connected with the other end of said recording cylinder; hydraulic liquid filling said recording cylinder and said upper and lower portions; means for mounting and driving a chart; and a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; and means for yieldably urging said arms to pivot outwardly and contact the well bore.

5. In a drill string terminating at its lower end in a bit for drilling a bore, a caliper assembly comprising inner and outer barrels inserted in said string above said bit, the inner barrel being retained within said outer barrel and telescopically engaged therewith, said barrels each having a liquid passage therethrough and said inner barrel having an annular series of apertures through its wall, the outer barrel sheathing said apertures when said barrels are in mutually retracted position; complimentary projections carried by said respective barrels and meshing when the latter are retracted, said meshed projections transmitting torque from said string to said bit during the drilling operation; latch means for releasably maintaining said barrels mutually retracted; and a calipering and recording tool having an annular series of caliper arms pivoted at one end thereto and having measurement recording means operatively associated with said arms, said tool being pumped downwardly in said string when the drilling operation is concluded and tripping said latch means to permit elongation of said telescoping barrels to unsheath said apertures, said tool lodging in said inner barrel with said caliper arms engaging said well bore through said apertures, whereby upon withdrawal of said string upwardly in the well said arms will measure the diameter of said bore and transmit said measurements to said recording means.

6. In a device as set forth in claim 5, said tool having an annular series of spaced bosses around its upper end; said inner barrel having a conically flared mouth at the upper end of its liquid passage, and said bosses engaging said flared mouth to arrest downward movement of said tool, the latter being smaller in diameter than said liquid passage to permit liquid circulation to be maintained at all times through the drill string.

7. In a device as set forth in claim 5, anti-friction bearing means carried by said barrels and operatively engaging when the latter are in elongated position, where by said supporting string can be freely rotated with respect to said inner barrel, said tool being capable of riding upwardly in said inner barrel to permit the drill string to be lowered in the bore through short distances during withdrawal therefrom without damage to said arms.

8. In a device as set forth in claim 5, said tool comprising a body, said arms being axially disposed with respect thereto and said arms each having a cam surface at its pivoted end; a cam follower contacting each cam surface and reciprocably mounted adjacent to an associated cylindrical bore in the body; a measuring piston in each cylindrical bore connected for unitary axial displacement with its associated cam follower, each measuring piston dividing each cylindrical bore into upper and lower portions, the respective upper portions being interconnected and the respective lower portions being interconnected; a recording piston movable within a recording cylinder, said upper portions being connected with one end of said recording cylinder, and said lower portions being connected with the other end of said recording cylinder; hydraulic liquid filling said recording cylinder and said upper and lower portions; means for mounting and driving a chart; and a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; and means for yieldably urging said arms to pivot outwardly and contact the well bore.

9. In a device as set in claim 8, spring finger means in the liquid passage of said inner barrel to engage a curved recess in the side of the tool; said engagement turning the tool as it enters said liquid passage to align said arms with said apertures.

10. In a drill string terminating at its lower end in a bit for drilling a bore, a caliper assembly comprising inner and outer barrels inserted in said string above said bit, the inner barrel being retained within said outer barrel and telescopically engaged therewith, said barrels each having a liquid passage therethrough and said inner section having apertures through its wall; projections carried by said respective barrels and meshing when the latter are retracted, said meshed projections transmitting torque from said string to said bit during the drilling operation; latch means for releasably maintaining said barrels mutually retracted; and a calipering and recording tool having caliper arms, and having measurement recording means operatively associated with said arms, said tool being pumped downwardly in said string when the drilling operation is concluded and tripping said latch means to permit elongation of said telescoping barrels; said tool" lodging in said inner'barrel with said caliper arms engaging'saidwell bore through said apertures, whereby upon'withdrawal of said string upwardly-in' the well said arms will measure the diameter of said bore andtransmit saidmeas'urements to said recordingmeans;

P1. In a deviceasset forth'in claim said tool having an annular'series of spaced bosses around its upper end; said inner barrel having a conically flared mouth at the upper end of its liquid passage, and said bosses engaging said flared mou'tn'to'arres't downward rriovem'en't of said tool.

12. In a device as set forth in claim 10, said tool being capable of riding upwardly in said inner barrel to permit the drill string to be lowered in the bore through short distances during withdrawal therefrom without damage to said arms.

13. In a device as set forth in claim 10, said tool being smaller in diameter than the liquid pasage through the inner barrel to permit liquid circulation to be maintained at all times through the drill string.

14. In a device as set forth in claim 10, antifriction bearing means carried by said barrels and operatively engaging when the latter are in elongated position whereby said supporting string can be freely rotated with respect to said inner barrel and associated arms engaging the bore.

15. In a device as set forth in claim 10, said tool com prising a body, said caliper arms being pivoted to said body and said arms each having a cam surface; a cam follower contacting each cam surface and reciprocably mounted in an associated cylindrical bore in the body; a measuring piston in each cylindrical bore connected for unitary axial displacement with its associated cam fol lower, the respective cylindrical bores being intercon nected; a recording piston movably mounted in a re cording cylinder, said cylindrical bores being connected with said recording cylinder; hydraulic liquid filling said recording cylinder and said cylindrical bores; means for mounting and driving a chart; a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; and spring means yieldably urging said followers against said cams to thereby urge the arms to pivot outwardly and contact the well bore.

16. In a device as set forth in claim 15, spring finger means in the liquid passage of said inner barrel to engage a curved recess in the side of the tool, said engagement turning the tool as it enters said liquid passage to align said arms with said apertures.

17. In a drill string terminating at its lower end in a bit for drilling a bore, a caliper assembly comprising a barrel inserted in said string above the bit, said barrel having a liquid passage therethrough and having an annu lar series of apertures through its wall; and a calipering and recording tool having an annular series of caliper arms each pivoted at its upper end thereto and having measurement recording means operatively associated with said arms, said tool being pumped downwardly in said string when the drilling operation is concluded and lodging in said barrel with said caliper arms engaging said well bore through said apertures, whereby upon withdrawal of said string upwardly in the well said arms will measure the diameter of said bore and transmit said measurements to said recording means.

18. In a device as set forth in claim 17, said tool having an annular series of spaced bosses around its upper end and said barrel having a conically flared mouth at the upper end of its liquid pasage, said bosses engaging said flared mouth to arrest downward movement of said tool, and said tool being smaller in diameter than said passage to permit said tool to ride up in said barrel I0 and permit the drillstringto be lowered in the bore through short distances during; withdrawal therefrom without damage to said arms.-

1'9. Irra device asset 'forth' in claim 17, said tool comprisirig a body, said armsbeing. axially disposed and each havingsa cam surface at its pivoted end; a cam follower contacting. each cam surface and reciprocably mounted adjacent to an' associated cylindrical bore in the body; a-measuring piston in each cylindrical bore connected for unitary axial displacement with its associated cam follower, theresp'e'ctive cylindrical b'o're's being interconnected; a recording piston movably mounted in a recordingicyl inder, said cylindrical bores being connected with said recording cylinder; hydraulic liquid filling said recording cylinder and said cylindrical bores; means for mounting and driving a chart; a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; and spring means yieldably urging said followers against said cams to thereby urge the arms to pivot outwardly and contact the well bore.

20. As an article of manufacture, an outer barrel; an inner barrel, the latter being retained within the former and telescopically engaged therewith, said barrels each having a central passage therethrough and said inner barrel having an annular series of spaced apertures through its wall communicating with its passage; complementary projections carried by said respective barrels and meshing when the latter are retracted; latch means for releasably maintaining said barrels mutually retracted, the outer barrel sheathing said apertures in this position; and antifriction bearing means carried by said barrels and operatively engaging when the latter are in elongated position.

21. The method of calipering a well bore at the conclusion of a drilling operation and during Withdrawal of the drill string from the bore, including the steps of inserting in the drill string before the drilling operation an apertured pipe; and after completion of the drilling operation lowering a calipering tool through the drill string into the apertured pipe; and withdrawing the drill string and calipering tool upwardly in the bore while calipering the latter through the apertured pipe.

22. The method of calipering a well bore at the conclusion of a drilling operation and during Withdrawal .of the drill string from the bore, including the steps of inserting in the drill string before the drilling operation a normally sheathed apertured pipe; and after completion of the drilling operation lowering a calipering tool through the drill string into the apertured pipe; unsheathing the apertured pipe; and withdrawing the drill string, apertured pipe and calipering tool upwardly of the bore while simultaneously calipering the bore through the apertured pipe.

23. A calipering tool comprising a calipering sub adapted to be inserted in a well string immediately above the drill bit, a plurality of apertures in said sub, a recording means adapted to be dropped through the drill string and seat in said sub, a plurality of calipering arms pivotally attached to the lower end of said recording means and adapted to project through said apertures into contact with the well bore when said recording means seats in said sub, means connecting said arms to said recording means whereby said recording means will continuously record the well diameter as the well string is withdrawn from the well.

24. A caliper assembly comprising a calipering sub adapted to be inserted in said drill string immediately above the drill bit, said sub comprising an outer tubular member adapted to be fastened to a drill string, an inner tubular member telescopically received within said outer member, a plurality of axially elongated apertures in said inner member normally shielded by said outer member when said members are mutually retracted, latch means for normally retaining said members in mutually retracted relation, recording means adapted to be dropped through the well string into seating engagement with said inner member, means on said recording means adapted to trip said latch means and permit extension between said members to uncover said apertures, a plurality of caliper arms pivotally attached to said recording means adapted to pivot outwardly through said apertures into contact with the bore wall, means biasing said arms outwardly, means connecting said arms to said recording means whereby said recording means will continuously record the well diameter as the well string is withdrawn from the well.

References Cited in the file of this patent UNITED STATES PATENTS Rieber Nov. 30, 1934 Kinley Dec. 14, 1937 Barnett Feb. 18, 1941 Moore Feb. 8, 1944 Chambers May 9, 1944 Millikan Feb. 19, 1946 Arps Oct. 3, 1950 Chaney et al. Sept. 11, 1951 FOREIGN PATENTS Great Britain Mar. 27, 1903 

